1. Field of the Invention
The present invention relates generally to six-sigma (6σ) optimization models and, more particularly, to a six-sigma model which incorporates the voice of the customer and product design into the overall optimization process.
2. Background Art
In the context of manufacturing optimization, sigma (σ) is a statistical unit of measure that reflects a level of manufacturing capability. Table 1 contains an exponential scale for quantifying manufacturing capability based on a conventional 6σ philosophy.
TABLE 1DEFECTS PER MILLIONσOPPORTUNITIES (DPMO)% SUCCESS63.499.99966523399.97746,21099.38366,80793.322308,53769.2
Notably, a slight increase in sigma level results in an exponential reduction in the number of defects per million manufacturing opportunities. In accord with traditional notions of 6σ manufacturing capability, a manufacturer does not attain a “best-in-class” (BIC) status until a 6σ capability level (i.e., <3.4 DPMO) is attained.
In many cases, a manufacturer's ability to transcend the 5σ level of success is hampered by the fact that 70-80% of product defects are a direct or indirect result of designed-in quality problems (i.e., problems that cannot be resolved by an increase in manufacturing capabilities alone). Accordingly, to attain a 6σ level of success, the optimization methodology should include elements of product design. Most models for 6σ optimization, however, do not incorporate the necessary design aspect of optimization. Conventional 6σ models involve the steps of measuring existing manufacturing capabilities, analyzing mechanical opportunities for decreasing variability associated with the existing manufacturing process, improving the capabilities of the manufacturing process by adopting the most cost-effective improvement opportunities, and controlling the manufacturing process to minimize variability.
Furthermore, although a few 6σ models have attempted to incorporate product design into product optimization, these models seek to enhance the robustness of product design without incorporating a detailed analysis of the voice of the customer. Although existing 6σ design optimization models including design optimization may improve product robustness, they do not analytically focus on opportunities for increasing product robustness which are most critical to customer satisfaction. Put another way, conventional 6σ design optimization models arbitrarily increase product robustness where possible without quantitatively and qualitatively weighing whether doing so will ultimately increase customer satisfaction beyond a negligible level.